Reflective electrophoretic display with laterally adjacent color cells using a reflective panel

ABSTRACT

An ambient light reflective color electrophoretic display is comprised of a plurality of color pixels; each comprised of at least two electrophoretic cells. Each cell is comprised of a suspension of charged, black or colored light-absorbing pigment particles in a light-transmissive fluid. Each cell is also comprised of a light-transmissive front window, at least one non-obstructing counter electrode, at least one non-obstructing collecting electrode, a light-reflective panel, and a color filter medium. The cells of different colors are in a laterally adjacent relationship to each other and the charged pigment particles are responsive to the electrodes. The filter medium in each cell can be a light-transmissive color filter element or a light-reflective colored surface or the pigment suspension fluid can be colored and serve as the filter medium.

RELATED APPLICATION

This application is related to concurrently filed co-pendingapplications Ser. Nos. 09/154,119; 09/154,364; and 09/154,626.

TECHNICAL FIELD

The present invention relates to electrophoretic cells that form anelectrophoretic display. In particular the invention relates to a cellconfiguration for use in a color electrophoretic display operating in alight-reflective mode.

BACKGROUND OF THE INVENTION

An electrophoretic cell is a cell comprised of pigment particlessuspended in a fluid and uses electrophoresis to switch between thefollowing two states:

Distributed State:

Particles are positioned to cover the horizontal area of the cell. Thiscan be accomplished, for example, by dispersing the particles throughoutthe cell, by forcing the particles to form a layer on the horizontalsurfaces of the cell, or by some combination of both.

Collected State:

Particles are positioned to minimize their coverage of the horizontalarea of the cell, thus allowing light to be transmitted through thecell. This can be accomplished, for example, by compacting the particlesin a horizontal area that is much smaller than the horizontal area ofthe cell, by forcing the particles to form a layer on the verticalsurfaces of the cell, or by some combination of both.

The electrophoretic cell can serve as a light valve since thedistributed and collected states can be made to have different lightabsorbing and/or light scattering characteristics. As a result, anelectrophoretic cell can be placed in the light path between a lightsource and a viewer and can be used to regulate the appearance of apixel in a display. The basic operation of reflective electrophoreticcells along with the examples of various electrode arrangements isdescribed in U.S. Pat. No. 5,745,094.

Reflective color displays are known that use liquid crystals inconjunction with a fixed polarizer element to control the intensity oflight reflected from each pixel. Since polarizers absorb the fraction oflight whose polarization is not aligned with their active axis, andsince this absorption varies with the angle of incidence, displays basedon their use suffer from both limited reflectivity and viewing angle.

Other reflective color displays are known that use a solution of adichroic dye in single or multiple layers of either a nematic orcholesteric liquid crystal material. Using a single nematic layerrequires the use of a fixed polarizer element and therefore suffers fromthe aforementioned limitations. Using one or more cholesteric layers, ormore than one nematic layer, eliminates the need for a fixed polarizerelement and increases the achievable reflectivity. This approach stillrelies on the selective absorption of polarized light and, as a result,the contrast changes with viewing angle.

Other reflective color displays are known that use scattering liquidcrystal materials, such as polymer-dispersed liquid crystal materials orscattering-mode polymer stabilized cholesteric texture materials, tocontrol the intensity of light reflected from each pixel by switchingbetween a turbid state and a uniform state. Since these materials onlyweakly scatter light in their turbid state, reflective displays based onthem have a low diffuse reflectance and therefore also suffer from lowbrightness.

Other reflective color displays are known that use reflecting liquidcrystal materials, such as reflective-mode polymer-stabilizedcholesteric texture materials or holographic-polymer-dispersed liquidcrystals, to control the both the intensity and color of reflected lightreflected from each pixel via diffraction effects. Since these depend ondiffraction effects, it is difficult to simultaneously achieve largeviewing angle, high reflectance, and angle independent color.

Reflective color electrophoretic displays have been proposed in theprior art. Japanese Patent No. JP 1267525 assigned to Toyota Jidosha KKdescribes an electrophoretic display having colored (blue and yellow)particles with different zeta potentials in a solution of red dye togive a multicolored (yellow, green and red) display. When a certainvoltage is applied to the pixels, the yellow particles are pulled to thefront transparent electrode and the viewer sees yellow. At a highervoltage, the blue particles are also pulled to the front electrode andthe viewer sees green. When the particles are pulled off the transparentelectrode, the colors of the particles are hidden by the dye solutionand the viewer sees red.

Evans, et al., in U.S. Pat. No. 3,612,758, describe a reflectiveelectrophoretic display having pigment particles of a single color in acontrasting dye solution. In this scheme, under the influence of anelectric field, the particles migrate to a front transparent electrodeand the viewer sees the color of the particles. When the field isreversed, the particles migrate away from the front transparentelectrode, are hidden in the dye solution, and the viewer sees the colorof the dye solution.

In the two electrophoretic display patents above, color contrast andreflectance depend on the presence or absence of particles at the frontwindow. Since the dye solution can not be completely removed from thespace between the particles when they are at the front window, displaysbased on this approach do not produce highly contrasted images andgenerally have a low reflectance.

Hou, in WO 94/28202, describes a dispersion for a reflectiveelectrophoretic display comprised of two differently colored particlesthat are oppositely charged. The polarity of the voltage applied to thecell determines the polarity of the particle attracted to the fronttransparent electrode, and hence determines the color seen by theviewer. Since the viewer sees either one of two colors, this approachproduces monochrome images and therefore has a limited color gamut.

Di Santo, et al., in U.S. Pat. No. 5,276,438, disclose a reflectiveelectrophoretic display in which a mesh screen, disposed behind thefront window and covering the viewing area of the display, is usedeither with or without a dyed suspension fluid to hide particles of asingle color from the viewer. When the particles are positioned in frontof the mesh, the viewer sees the color of the particles. When theparticles are positioned behind the mesh, the viewer sees a mixture ofthe mesh and particle colors. As a result, the contrast produced by thisapproach is limited by the open area of the mesh. In addition, thisapproach produces monochrome images and therefore has a limited colorgamut.

There is a continuing need in the art for a low-power reflective colorelectrophoretic display with high reflectance, high image contrast, andlarge color gamut. It is therefore an object of the present invention toprovide a low-power, reflective color electrophoretic display havingimproved reflectance, image contrast, and color gamut. Other objects andadvantages will become apparent from the following disclosure.

SUMMARY OF THE INVENTION

The present invention relates to a reflective electrophoretic colordisplay. The display is intended to be viewed while illuminated from thefront by ambient light and to operate without the need of a backlight.The display is comprised of many picture elements or pixels located inlateral adjacency in a plane. The pixels are comprised of two or moresub-pixels, or cells, which are also located in lateral adjacency in aplane. Each cell reflects a different color. The color of a pixel isdetermined by the additive mixture of the colors reflected by each ofits respective cells.

Each cell is comprised of a light-transmissive front window, at leastone non-obstructing counter electrode, at least one non-obstructingcollecting electrode, a light-reflective panel, and a color filtermedium. Each cell also contains a suspension of charged, light-absorbingpigment particles in a light-transmissive fluid.

The amount of colored light reflected by each cell is controlled by theposition of the pigment particles within the cell. The position, inturn, is directed by the application of appropriate voltages to thecollecting and counter electrodes. When the pigment particles arepositioned in the path of the light, the light is significantlyattenuated before emerging from the front window, and the viewer seesdim color or black. When the pigment particles are substantially removedfrom the path of the light, light can be reflected back through thefront window to the viewer without significant attenuation, and theviewer sees the color transmitted by the color filter medium. The colorfilter medium can, for example, be a light-transmissive colored filterelement, a colored light-reflecting panel, or the pigment suspensionfluid itself can be colored and serve as the color filter medium.

A more thorough disclosure of the present invention is presented in thedetailed description that follows and from the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a and 1 b are sectional views of a first embodiment of anelectrophoretic display cell of the present invention.

FIGS. 2a and 2 b are sectional views of a second embodiment of anelectrophoretic display cell of the present invention.

FIGS. 3a and 3 b are sectional views of a third embodiment of anelectrophoretic display cell of the present invention.

FIGS. 4a and 4 b are sectional views of a fourth embodiment of anelectrophoretic display cell of the present invention.

FIGS. 5a and 5 b are sectional views of a fifth embodiment of anelectrophoretic display cell of the present invention.

FIGS. 6a and 6 b are sectional views of a sixth embodiment of anelectrophoretic display cell of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a reflective electrophoretic colordisplay. The display is intended to be viewed while illuminated from thefront by ambient light and to operate without the need of a backlight.The display is comprised of many picture elements or pixels located inlateral adjacency in a plane. The pixels are comprised of two or moresub-pixels, or cells, which are also located in lateral adjacency in aplane. Each cell reflects a different color. The color of a pixel isdetermined by the additive mixture of the colors reflected by each ofits respective cells.

Each cell is comprised of a light-transmissive front window, at leastone non-obstructing counter electrode, at least one non-obstructingcollecting electrode, a light-reflective panel, and a color filtermedium. Each cell also contains a suspension of charged, light-absorbingpigment particles in a light-transmissive fluid.

The amount of colored light reflected by each cell is controlled by theposition of the pigment particles within the cell. The position, inturn, is directed by the application of appropriate voltages to thecollecting and counter electrodes. In the extreme these produce twostates: a distributed state and a collected state. In the distributedstate, the pigment particles are positioned in the path of the light sothat the light is significantly attenuated before exiting the frontwindow, and the viewer sees dim color or black. In the collected state,the particles are substantially removed from the path of the light sothat light can be reflected back through the front window to the viewerwithout significant attenuation, and the viewer sees the colortransmitted by the color filter medium.

The suspension is minimally comprised of pigment particles and a lighttransmissive fluid. The properties of the suspension are preferablyhighly stable with both time and use. The suspension is preferablyhighly resistant to agglomeration, flocculation, and sticking to thesurfaces in the cell, even after being compacted and re-dispersed manytimes. The suspension preferably doesn't react with the surfaces in thecell. The specific gravity of the pigment particles and the fluid arepreferably similar. The pigment particles preferably acquire a singlepolarity when placed in suspension.

Optionally, other components may be added to the suspension such ascharge control additives, dispersants, and surfactants to improve theperformance of the suspension. Suitable additives include sodiumdioctylsulfosuccinate, zirconium octoate, and metal soaps such aslecithan, barium petronate, calcium petronate, alkyl succinimide, ironnaphthenate, and polyethylene glycol sorbitan stearate.

The suspension fluid must transmit the color of light transmitted by thecolor filter medium. The fluid can be colorless or colored with either adye and/or pigment. The fluid preferably has minimum solvent action onthe pigments and does not react with the surfaces in the cell. The fluidis preferably dielectric and substantially free of ions. The fluidpreferably has a low viscosity. The fluid can be a mixture of fluids.Suitable fluids include silicone fluids such as hexamethyldisiloxane,octamethyltrisiloxane, decamethyltetrasiloxane, and otherpoly(dimethylsiloxane)s. Suitable fluids also include hydrocarbons suchas decane, dodecane, tetradecane, xylene, Sohio odorless solvent (akerosene fraction available from Exxon Company), toluene, hexane andIsopar® C, E, G, H, K, L, M, and V and Norpar® 12, 13, and 15 (branchedand linear saturated aliphatic hydrocarbons available from ExxonCompany).

The pigment particles must absorb the color of light transmitted by thecolor filter medium. The pigment particles can be black or colored.Suitable colors include red, green, blue, cyan, magenta, yellow, or thelike. Suitable classes of inorganic pigments include:

Cadmium Red

Cadmium sulfo-selenide (black)

Carbon Black

Chromium oxide (green)

Iron oxides (black)

Iron oxides (red)

Lead chromate (yellow)

Manganese dioxide (brown)

Silicon monoxide (reddish brown)

Sulfur (yellow)

Vermilion Red

Suitable classes of organic pigments include:

Anthracene (fluorescent blue, fluorescent yellow)

Anthraquinone (blue, red, yellow)

Azonaphthols (magenta)

Azopyridone (yellow)

Heterocyclic Azo (cyan, magenta)

Methine (yellow)

Nigrosines (black)

Phthalocyanine (blue, green, cyan)

Quinacridone (magenta)

Suitable opaque pigment particles include:

Anric Brown (C.I. Pigment Brown 6)

Cabot Mogul L (black)

C.l. Direct Yellow 86

C.l. Direct Blue 199 (cyan)

C.l. Food Black 2

Dalama® Yellow (Pigment Yellow 74)

Hansa® Yellow (Pigment Yellow 98)

Indo® Brilliant Scarlet (Pigment Red 123)

Monastral® Green G (C.l. Pigment Green 7)

Monastral® Blue B (C.l. Pigment Blue 15)

Monastral® Blue G (C.l. Pigment Blue 15)

Monastral® Green B (C.l. Pigment Green 7)

Paliotol® Black L0080 (C.l. Pigment Black 1)

Permanent Rubine F6Bl3-1731 (Pigment Red 184)

Pigment Scarlett (C.l. Pigment Red 60)

Quindo® Magenta (Pigment Red 122)

Stirling NS N 77Y (Pigment Black 7)

Toluidine Red B (C.l. Pigment Red 3)

Toluidine Red Y (C.l. Pigment Red 3)

Toluidine Yellow G (C.l. Pigment Yellow)

Watchung® Red B (C.l. Pigment Red 48)

Other suitable pigment particles will be known to those skilled in theart such as those disclosed in U.S. Pat. Nos. 5,200,289 and 4,631,244.

The collecting and counter electrodes in each cell are constituted orsized or positioned to be non-obstructing. This means that in thecollected state, neither the particle coated collecting electrode northe counter electrode unacceptably interferes with the passage of thedesired color of light as it travels through the cell, i.e.substantially all of the incident light of the desired color isreflected from the cell. A non-obstructing collecting electrode can berealized by allowing it to occupy only a small fraction of thehorizontal area of the cell by, for example, forming it into a narrowline or a small pedestal. It can also be realized by disposing it alonga vertical wall in the cell. A non-obstructing counter electrode can berealized similarly or, alternatively, by coating the inside surface ofthe front window or the rear panel with a layer of conductive,light-transmissive material such as indium tin oxide. Alternatively, arear panel with a light reflecting metallic surface can also serve asthe counter electrode.

There can be one or more non-obstructing collecting electrodes and oneor more non-obstructing counter electrodes in each cell and eitherelectrode can be common to more than one cell. The electrodes arepreferably good conductors (e.g. aluminum, chromium, copper, nickel),can be light transmissive (e.g. indium tin oxide), and can be disposedvertically and/or horizontally in the cell.

Various electrode arrangements for a reflecting electrophoretic cell aredescribed in U.S. Pat. No. 5,745,094, which is incorporated herein byreference.

The light reflective panel can be colored or colorless provided itreflects the color of light transmitted by the color filter medium. Thepanel can be mirrored to reflect all visible wavelengths (e.g. coatedwith aluminum, chromium, or silver), or mirrored to reflect selectedvisible wavelengths (e.g. coated with a dielectric stack).Alternatively, the panel can be pigmented white or can be colored witheither a pigment or a dye. The panel preferably has a high reflectivityfor the color of light transmitted by the color filter medium. Thereflected light is preferably diffused either by the reflective panelitself or by a separate element.

The color filter medium selects the color reflected by each cell. Thecolor filter medium can, for example, be a light-transmissive coloredfilter element disposed across the horizontal area of the cell, eitherabove the suspension or below the suspension on top of thelight-reflecting panel. An appropriately colored pigment suspensionfluid, a colored light-reflecting panel, a color diffuser, or a paintedsurface can also serve as the color filter medium.

The following example is a detailed description of a display of thepresent invention. The details fall within the scope of, and serve toexemplify, the more general description set forth above. The example ispresented for illustrative purposes only, and is not intended as arestriction on the scope of the invention.

Referring to FIGS. 1a and 1 b through 6 a and 6 b there are illustratedpreferred embodiments of electrophoretic display cells in accordancewith the present invention. Each cell 14, 16, and 18 generally comprisesa front light-transmissive window 2, a horizontal rear panel 4, and arespective light-reflective surface 6 a, 6 b, and 6 c facing the frontwindow 2. Each cell 14, 16, 18 has a non-obstructing collectingelectrode 8 and a light-transmissive counter electrode 20 disposedwithin the cell and spaced apart as illustrated. Each cell 14, 16, and18 also has a suspension comprised of pigment particles 10 a, 10 b, and10 c, respectively, in a light-transmissive fluid 12 a, 12 b, and 12 c,respectively, in the space between the counter electrode 20 and therespective light-reflective surface 6 a, 6 b, and 6 c. Thelight-transmissive fluids 12 a, 12 b, 12 c in cells 14, 16, and 18,respectively, are separated by barriers 22.

Electrophoretic cell 14 is associated with a red filter medium,electrophoretic cell 16 is associated with a green filter medium, andelectrophoretic cell 18 is associated with a blue filter medium. Thethree laterally adjacent cells 14, 16, and 18 create an electrophoreticreflective color pixel 26. There are also shown two walls 24 tofiguratively demarcate the sides of each pixel 26. These side pixelwalls 24 are shown for illustrative purpose and may not be present inthe actual embodiment.

In the embodiments illustrated in FIGS. 1a and 1 b through 6 a and 6 b,the collecting electrodes 8 represent individually addressableconducting lines whose horizontal area is much smaller than thehorizontal area of the cell. The counter electrode 20 represents alight-transmissive conductor and is shared by all the cells 14, 16, and18 in the pixel 26. The distributed state of the cells 14, 16, and 18are illustrated as one in which the respective particles 10 a, 10 b, and10 c are generally uniformly dispersed throughout their respectivesuspension fluids 12 a, 12 b, 12 c. The collected state of the cells 14,16, and 18 are illustrated as one in which the particles haveaccumulated on their respective collecting electrodes 8, as shown forexample, by cell 18 in FIG 1 a and cells 14 and 16 in FIG. 1b.

The arrangement of FIGS. 1a and 1 b includes a red filter element 30 incell 14, a green filter element 32 in cell 16, and a blue filter element34 in cell 18. These light-transmissive filter elements 30, 32, 34 arerespectively located across the lower surface of the front window 2,between the front window 2 and the counter electrode 20, and are inlateral adjacency in a plane with each other. In both FIGS. 1a and 1 bthe pigment particles 10 a, 10 b, and 10 c are black.

In FIG. 1a, cells 14 and 16 are shown in the distributed state. Sincethe black absorbing particles 10 a and 10 b are distributed over thehorizontal area of these cells, incident ambient light transmitted bythe filters 30 and 32 is substantially absorbed before it reaches theviewer. Consequently, cells 14 and 16 appear black to the viewer.

Cell 18 of FIG. 1a is shown in the collected state. Since the blackabsorbing particles 10 c are collected in a small horizontal area ofthis cell, and since the suspension fluid 12 c transmits the color oflight transmitted by the filter 34, incident ambient light transmittedby the blue filter 34 can both substantially reach and reflect from thereflective surface 6 c back to the viewer.

Consequently, cell 18 appears blue to the viewer. Since cells 14 and 16reflect substantially no light and cell 18 reflects blue light, thepixel 26 will appear blue to the viewer.

FIG. 1b shows the complementary state of FIG. 1a—cells 14 and 16 are inthe collected state and cell 18 is in the distributed state. As aresult, cells 14 and 16 will reflect red and green light, respectively,and cell 18 will reflect substantially no light. Consequently, the pixel26 reflects both red and green light and will appear yellow to theviewer.

FIGS. 2a and 2 b illustrate an arrangement similar to that illustratedin FIGS. 1a and 1 b. The difference is that instead of using blackpigment particles 10 a, 10 b, and 10 c, the pigment particles 10 aassociated with the red filter 30 in cell 14 are cyan, the pigmentparticles 10 b associated with the green filter 32 in cell 16 aremagenta, and the pigment particles associated with the blue filter 34 incell 18 are yellow. Since the respective pigment colors arecomplementary to their associated filter colors, the pigment particlesabsorb the color of light transmitted by their associated color filterso that the cell, in its distributed state, will reflect substantiallyno light.

In the arrangement illustrated in FIGS. 3a and 3 b, the filter medium isconstituted by a red colored suspension fluid 12 a in cell 14, a greencolored suspension fluid 12 b in cell 16, and a blue colored suspensionfluid 12 c in cell 18. There are no separate filter elements 30, 32, and34. The pigment particles 10 a, 10 b, and 10 c are black and thereforeabsorb the color of the light transmitted by the colored suspensionfluid. In the distributed state, the particles absorb the color of thelight transmitted by the colored fluid, and the cell appears dark orblack. In the collected state, light can both reach and emerge from therespective light-reflecting surface 6 a, 6 b, 6 c and the color of therespective suspension fluid 12 a, 12 b, 12 c in the cells 14,16, 18 isreflected.

The arrangement illustrated in FIGS. 4a and 4 b is similar to thatillustrated in FIGS. 3a and 3 b. The difference is that instead of usingblack pigments particles 10 a, 10 b, and 10 c, the pigment particles 10a associated with the red suspension fluid 12 a in cell 14 are cyan, thepigment particles 10 b associated with the green suspension fluid 12 bin cell 16 are magenta, and the pigment particles 10 c associated withthe blue suspension fluid 12 c in cell 18 are yellow. Since therespective pigment colors are complementary to their associatedsuspension fluid colors, the pigment particles absorb the color of lighttransmitted by their associated suspension fluid so that the cell, inits distributed state, will reflect substantially no light. In thiscase, for maximum visual contrast, the distributed state is preferablyone that prevents the viewer from directly seeing the particles. Forexample, the distributed state in this case is preferably not one inwhich the particles are distributed in a slab along the surface of thecounter electrode 20.

In the arrangement illustrated in FIGS. 5a and 5 b, the filter medium isconstituted by a light-reflecting surface 6 a in cell 14 that onlyreflects red light, a light-reflecting surface 6 b in cell 16 that onlyreflects green light, and a light-reflecting surface 6 c in cell 18 thatonly reflects blue light. The pigment particles 10 a, 10 b, and 10 c areblack and therefore absorb the color of the light reflected by thecolored surface. In the distributed state, the particles absorb thecolor of the light reflected by the colored surface, and the cellappears dark or black. In the collected state, light can both reach andemerge from the respective light-reflecting colored surface 6 a, 6 b, 6c and the color of the respective light-reflecting colored surface 6 a,6 b, 6 c in the cells 14, 16, 18 is reflected.

The arrangement illustrated in FIGS. 6a and 6 b is similar to thatillustrated in FIGS. 5a and 5 b. The difference is that instead of usingblack pigments particles 10 a, 10 b, and 10 c, the pigment particles 10a associated with the red reflecting surface 6 a in cell 14 are cyan,the pigment particles 10 b associated with the green reflecting surface6 b in cell 16 are magenta, and the pigment particles 10 c associatedwith the blue reflecting surface 6 c in cell 18 are yellow. Since therespective pigment colors are complementary to their associated coloredsurface colors, the pigment particles absorb the color of lightreflected by their associated colored surface so that the cell, in itsdistributed state, will reflect substantially no light. In this case,for maximum visual contrast, the pigment particles preferably do notsubstantially scatter or reflect light.

Although this invention has been described with respect to specificembodiments, the details thereof are not to be construed as limitationsfor it will be apparent that various embodiments, changes, andmodifications may be resorted to without departing from the spirit andscope thereof. Further, it is understood that such equivalentembodiments are intended to be included within the scope of thisinvention.

For example, other embodiments of this invention can use different colorcombinations for the cells within the pixel. As another example, theparticles in FIGS. 2a-2 b, 4 a-4 b, and 6 a-6 b need not be a colorcomplementary to the color of their associated color filter medium, theyneed only be a color that absorbs the color of light transmitted bytheir associated color filter medium.

In addition, some components in the illustrations above may not benecessary or could be modified in other embodiments. For example, in theembodiments illustrated in FIGS. 1a-1 b, and in FIGS. 5a-5 b, thebarriers 22 are not necessary - the cells 14, 16, and 18 can share thesame suspension. In the embodiments illustrated in FIGS. 2a-2 b, and inFIGS. 6a-6 b, the barriers 22 need only be impervious to the pigmentparticles - the cells 14, 16, and 18 can share the same suspensionfluid.

What is claimed is:
 1. An electrophoretic display having a plurality ofcells disposed between a light-transmissive front window and areflective rear panel, comprising: multiple pixels each formed bymultiple cells in a lateral adjacent arrangement relative to each other,each adjacent cell being between the front window and the reflectiverear panel, and each cell containing charged, light-absorbing pigmentparticles in a light-transmissive fluid; a non-obstructing collectingelectrode to substantially remove pigment particles in the respectivecells from the path of light through the cell; a non-obstructing counterelectrode cooperating with the collecting electrode to distribute thepigment particles in the respective cells to substantially block thepath of light from the light source; and a color filtering medium foreach respective cell, and wherein in three adjacent cells of each pixel,respectively, the color filter medium is red and the associatedparticles are cyan, the color filter medium is green and the associatedparticles are magenta, and the color filter medium is blue and theassociated particles are yellow.
 2. An electrophoretic display having aplurality of cells disposed between a light-transmissive front windowand a reflective rear panel, comprising: multiple pixels each formed bythree cells in a lateral adjacent arrangement relative to each other andeach cell being between a light transmissive front window and alight-reflecting rear panel; each cell containing charged,light-absorbing pigment particles in a light-transmissive fluid; anon-obstructing collecting electrode to substantially remove pigmentparticles in the respective cells from the path of light so that lightcan pass through the cell without significant attenuation; anon-obstructing counter electrode, cooperating with the collectingelectrode to distribute the pigment particles in the respective cells tosubstantially block the path of light; and in each pixel, a red colorfilter element located across the window in a first one of the cells, ablue color filter element located across the window in a second one ofthe cells, and a green color filter element located across the window ina third one of the cells.
 3. An electrophoretic display as claimed inclaim 2 wherein the particles are a color that absorbs the colortransmitted by the color filter element.
 4. An electrophoretic displayas claimed in claim 2 wherein the particles are black or colored andwherein the fluid is substantially light-transmitting.
 5. Anelectrophoretic display as claimed in claim 2 wherein the particles area color complementary to the color of the filter element.
 6. Anelectrophoretic display comprising: a light-transmissive front windowand a parallel, spaced-apart reflective rear panel, the front windowsand rear panels defining a group of color cells disposed in a lateraladjacent relationship relative to each other to form a pixel; adifferent colored light-transmissive fluid disposed between the frontwindow and the reflective rear panel in each respective cell of thepixel, thereby forming a respective color filter medium for therespective cell; a suspension including charged, light-absorbing pigmentparticles in the colored light-transmissive fluid of each cell; anon-obstructing collecting electrode associated with each cell, whichacts to substantially remove pigment particles from the light path sothat light traversing the colored fluid can reach the reflective rearpanel and emerge from the front window without significant attenuation;and a non-obstructing counter electrode associated with each cell, whichacts to position the pigment particles to substantially block the pathof light so that light traversing the colored fluid is significantlyattenuated before emerging from the front window, and wherein therespective collecting electrode and the respective counter electrode actin concert for respective cells to thereby position the particles in therespective cells.
 7. An electrophoretic display as claimed in claim 6wherein the particles are a color that absorbs the color transmitted bythe colored light-transmissive fluid.
 8. An electrophoretic display asclaimed in claim 6 wherein the particles are black or colored.
 9. Anelectrophoretic display as claimed in claim 6 wherein the particles area color complementary to the color of the colored light-transmissivefluid.
 10. An electrophoretic display as claimed in claim 6 wherein inthree adjacent cells of each pixel, respectively, the coloredlight-transmissive fluid is red and the associated particles are cyan,the colored light-transmissive fluid is green and the associatedparticles are magenta, and the colored light-transmissive fluid is blueand the associated particles are yellow.
 11. An electrophoretic displayhaving a plurality of cells, each disposed between a light-transmissivefront window and a reflective rear panel, a group of cells acting toform a pixel, the display comprising: a red color fluid cell, a greencolor fluid cell, and a blue color fluid cell located in lateraladjacency relative to each other; a suspension in each color fluid cellincluding charged, light-absorbing pigment particles in the coloredfluid, the fluid being a light-transmissive fluid; non-obstructingcollecting electrodes, at least one associated with each color cell,which act to substantially remove pigment particles from the light pathso that light can pass through the cell without significant attenuation;and non-obstructing counter electrodes, at least one associated witheach color cell, which act to position the pigment particles tosubstantially block the path of light so that light is significantlyattenuated before emerging from the front window, and wherein therespective collecting electrodes and the respective non-obstructingelectrodes act in concert for respective cells to thereby position theparticles in the respective cells.
 12. An electrophoretic displaycomprising a plurality of cells having a light-transmissive front windowand a reflective rear panel, and wherein a pixel comprises threeindividual cells, the cells being in lateral adjacency relative to eachother: a) the first cell comprising a suspension of charged pigmentparticles in a first colored fluid, the first colored fluid serving toact as a first color filter and the pigment particles absorbing thevisible light not absorbed by the first colored fluid; b) the secondcell comprising a suspension of charged pigment particles in a secondcolored fluid, the second colored fluid serving to act as a second colorfilter and the pigment particles absorbing the visible light notabsorbed by the second colored fluid; c) the third cell comprising asuspension of charged pigment particles in a third colored fluid, thethird colored fluid serving to act as a third color filter and thepigment particles absorbing the visible light not absorbed by the thirdcolored fluid; and wherein d) each cell includes: (i) a non-obstructingcollecting electrode acting to substantially remove pigment particlesfrom the path of light through the colored fluid so that the color ofthe fluid is visible to the viewer, and (ii) a non-obstructing counterelectrode cooperating with the collecting electrode to position thepigment particles in the path of light through the colored fluid so thatthe color of the fluid is not visible to the viewer.
 13. A display asclaimed in claim 12 wherein the first cell comprises a suspension ofcharged, black pigment particles in a red fluid, the second cellcomprises a suspension of charged, black pigment particles in a greenfluid, and the third cell comprises a suspension of charged, blackpigment particles in a blue fluid.
 14. A display as claimed in claim 12wherein the first cell comprises a suspension of charged, cyan pigmentparticles in a red fluid, the second cell comprises a suspension ofcharged, magenta pigment particles in a green fluid, and the third cellcomprises a suspension of charged, yellow pigment particles in a bluefluid.
 15. An electrophoretic display comprising a plurality of cells ina lateral adjacent arrangement and containing a suspension of charged,light-absorbing pigment particles in a light-transmissive fluid, eachcell comprising: a light-transmissive front window; a rear panel havinga light-reflective surface; a respective color filter element associatedwith the reflective rear panel for each cell; a non-obstructingcollecting electrode, disposed relative to the front window and thereflective rear panel, the collecting electrode acting to substantiallyremove pigment particles from the path of light so that light can reachand reflect from the rear panel and emerge from the front window withoutsignificant attenuation; a non-obstructing counter electrode acting toposition the pigment particles to substantially absorb ambient lighttraversing the cell and thereby substantially prevent the light fromemerging from the front window; and wherein the cells each respectivelycontain a suspension of charged, pigment particles that absorb the colorof the light transmitted by the color filter element.
 16. A display asclaimed in claim 15 wherein the pigment particles are black, and thefilter element for respective cells are red, green, and blue.
 17. Adisplay as claimed in claim 15 wherein the colors of the filters and therespective colors of the particles are complementary.
 18. A display asclaimed in claim 15 wherein, in three adjacent cells, respectively, thecolored pigment particles are cyan and the associated filter element isred, the colored pigment particles are magenta and the associated filterelement is green, and the colored pigment particles are yellow and theassociated filter element is blue.
 19. A display as claimed in claim 15wherein the filter elements for respective cells are incorporated aspart of the reflective rear panel.
 20. A display as claimed in claim 15wherein the filter elements for respective cells are colored andreflective rear panel elements.